Liquid crystal display device and fabricating method thereof

ABSTRACT

A liquid crystal display device includes a first substrate, a second substrate and a liquid crystal layer between the first and second substrates. The liquid crystal display device further includes a gate line on the first substrate, a first insulation film on the gate line, a data line crossing the gate line such that the data line and the gate line define a pixel region with a transmission area and a reflection area, a thin film transistor connected to the gate line and the data line, a storage capacitor including a storage line crossing the data line and an upper storage electrode connected to the thin film transistor, a second insulation film on the thin film transistor with a transmission hole defined through the second insulation film, a reflection electrode disposed on the second insulation film in the reflection area and connected to a portion of the upper storage electrode through the transmission hole, and a pixel electrode disposed in the pixel region and connected to the reflection electrode.

This is a divisional application of U.S. patent application Ser. No.11/143,587, filed Jun. 3, 2005, and further claims the benefit of theKorean Patent Application No. P2004-41136 filed in Korea on Jun. 5,2004, both of which are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a liquid crystal display device, andmore particularly, to a transflective thin film transistor substrate andmethod of fabricating the same.

2. Description of the Related Art

Liquid crystal display devices are generally classified into atransmissive type where a picture is displayed using light incident froma backlight unit, and a reflective type where a picture is displayed byreflecting external light such as a natural light. However, the powerconsumption of the backlight unit is high in the transmissive type, andthe reflective type depends on the external light so that it cannotdisplay a picture in a dark environment.

To resolve this problem, a transflective liquid crystal display deviceis increasingly being used, wherein the transflective liquid crystal canbe selected to be in a transmissive mode where the backlight unit isused or in a reflective mode where the external light is used. Thetransflective liquid crystal display device operates in the reflectivemode if the external light is sufficient and in the transmissive mode ifthe external light is not sufficient, thereby reducing the powerconsumption more than the transmissive liquid crystal display device butnot being restricted by external light levels unlike the reflectiveliquid crystal display device.

Generally, a transflective liquid crystal display panel of the relatedart, as shown in FIG. 1, includes a color filter substrate and a thinfilm transistor substrate which are bonded together with a liquidcrystal layer (not shown), and a backlight unit 60 arranged behind thethin film transistor substrate. Each pixel of the transflective liquidcrystal display panel is divided into a reflective area where areflective electrode 28 is formed, and a transmissive area where thereflective electrode 28 is not formed.

The color filter substrate includes an upper substrate 52, a blackmatrix (not shown), a color filter 54 formed on the upper substrate 52,a common electrode 56, and an alignment film (not shown) formedthereover. The thin film transistor substrate includes a lower substrate2, a gate line 4, a data line (not shown) formed on the lower substrate2 crossing the gate line 4 to define each pixel area, a thin filmtransistor connected to the gate line 4 and the data line, a pixelelectrode 32 formed at the pixel area and connected to the thin filmtransistor; and a reflection electrode 28 formed at a reflection area ofeach pixel to overlap the pixel electrode.

The thin film transistor includes a gate electrode 6 connected to thegate line 4; a source electrode 16 connected to the data line; a drainelectrode 18 facing the source electrode 16; an active layer 10overlapping the gate electrode 6 with a gate insulating film 8therebetween to form a channel between the source and drain electrodes16 and 18; and an ohmic contact layer 12 to make an ohmic contact withthe active layer 10, the source electrode 16, and the drain electrode18. The thin film transistor responds to the scan signal of the gateline 4, thereby causing a video signal on the data line to be chargedand maintained on the pixel electrode 32.

The reflection electrode 28 reflects an external light that is incidentthrough a color filter substrate toward the color filter substrate. Atthis moment, the surface of an organic film 24 formed under thereflection electrode 28 has an embossing shape, and the reflectionelectrode 28 on top of the organic film 24 also has the embossing shape,thereby increasing its reflection efficiency due to its dispersioneffect.

The pixel electrode 32 is connected via an upper storage electrode 20 tothe drain electrode of the thin film transistor, and the pixel electrode32 generates a potential difference with a common electrode 56 by thepixel signal supplied through the thin film transistor. The potentialdifference causes liquid crystal molecules having dielectric anisotropyto rotate, thereby controlling the transmissivity of the light thatpasses through a liquid crystal layer of each of the reflection area anda transmission area, and changing its brightness in accordance with thevideo signal.

In this case, a transmission hole 36 is formed in the relatively thickorganic film 24 at a transmission area so that the length of the lightpath going through the liquid crystal layer is the same in thereflection area as in the transmission area. As a result, a path thatambient light incident at the reflection area, i.e., a reflection lightRL, goes through the liquid crystal layer, then through the reflectionelectrode 28, and then through the liquid crystal layer in the liquidcrystal layer is the same in length as a path that the transmissionlight TL of a backlight unit 60, which is incident at the transmissionarea going through the liquid crystal layer. Thus, the transmissionefficiency becomes the same in both of the reflection mode and thetransmission mode.

The thin film transistor substrate further includes a storage capacitorconnected to the pixel electrode 32 to maintain the video signalsupplied to the pixel electrode 32 stable. The storage capacitor isformed with an upper storage electrode 20 overlapping a storage line 40with a gate insulating film 8 therebetween. Here, wherein the upperstorage electrode 20 is extended from the drain electrode 18 to connectto the pixel electrode 32 via a contact hole 34. The ohmic contact layer12 and the active layer 10 further overlap under the upper storageelectrode 20 in the process.

The thin film transistor substrate further includes a first passivationfilm 22 between the thin film transistor and the organic film 24; asecond passivation film 26 between the organic film 24 and thereflection electrode 28; and a third passivation film 30 between thereflection electrode 28 and the pixel electrode 32. Accordingly, thecontact hole 34 penetrates the first to the third passivation films 22,26 and 30, the organic film 24 and the reflection electrode 28 so thatthe pixel electrode 32 is connected to the upper storage electrode 20.

In such a transflective liquid crystal display panel, the thin filmtransistor substrate includes the semiconductor process and requires aplurality of mask processes. Thus, its manufacturing process iscomplicated so that it significantly increases the liquid crystaldisplay panel manufacturing cost.

Hereinafter, a fabricating method of the transflective thin filmtransistor substrate according to the related art will be described inreference with FIGS. 2A to 2F. As shown in FIG. 2A, in a first maskprocess, a gate pattern including the gate line 4, the gate electrode 6,and the storage line 40 is formed on the lower substrate 2.

A gate metal layer is formed on the lower substrate 2 by a depositionmethod such as sputtering. Subsequently, the gate metal layer ispatterned by a photolithography process using a first mask and anetching process, thereby forming the gate pattern including the gateline 4, the gate electrode 6, and the storage line 40. The gate metallayer is a single layered or double layered metal, such as Al, Mo, orCr.

As shown in FIG. 2B, the gate insulating film 8 is formed on thesubstrate 2 having the gate pattern. On the substrate 2 having the gateinsulating film 8, a semiconductor pattern having the active layer 10and the ohmic contact layer 12 formed, and a source/drain pattern havingthe data line, the source electrode 16, the drain electrode 18 and theupper storage electrode 20 are stacked by the second mask process.

The gate insulating film 8, an amorphous silicon layer, an amorphoussilicon layer with impurities doped thereto, and the source/drain metallayer are sequentially formed on the lower substrate 2 where the gatepattern is formed. The gate insulating film 8 is formed of an inorganicinsulating material such as silicon oxide SiOx or silicon nitride SiNx,and the source/drain metal layer is the single layered or double layeredstructure of the metal such as Al, Mo or the like.

A photoresist pattern is formed on top of the source/drain metal layerby a photolithography process using a second mask. In this case, adiffractive exposure mask having a diffractive exposure portion at achannel of the thin film transistor is used as the second mask. Thus,the photoresist pattern of the channel has a lower height than thesource/drain pattern portion. Subsequently, the source/drain metal layeris patterned by a wet etching process using the photoresist pattern toform the source/drain pattern that includes the data line, the sourceelectrode 16, the drain electrode 18 integrated with the sourceelectrode 16, and the storage electrode 20. Then, the amorphous siliconlayer doped with the impurities and the amorphous silicon layer aresimultaneously patterned by a dry etching process using the samephotoresist pattern, thereby forming the ohmic contact layer 12 and theactive layer 10. After removing the photoresist pattern havingrelatively low height at the channel by an ashing process, thesource/drain pattern and the ohmic contact layer 12 of the channel areetched by a dry etching process. Accordingly, the active layer 10 of thechannel is exposed to separate the source electrode 16 from the drainelectrode 18. Subsequently, the photoresist pattern remaining on thesource/drain pattern is removed by a stripping process.

As shown in FIG. 2C, a first passivation film 22 is formed on the gateinsulating film 8 where the source/drain pattern is formed, and anorganic film 24 is formed on top thereof by a third mask process. Here,the organic film 24 has a contact hole 34 and a transmission hole 36with the embossing shaped surface.

The first passivation film 22 and the organic film 24 are sequentiallyformed on the gate insulating film 8 where the source/drain pattern isformed. The first passivation film 22 is formed of the same inorganicinsulating material as the gate insulating film 8, and the organic film24 is of a photosensitive organic material, such as an acrylic resin.

Then, the organic film 24 is patterned by a photolithography processusing the third mask, thereby forming an open hole 35 and thetransmission hole 36 which penetrate the organic film 24 incorrespondence to the transmission portion of the third mask. At thismoment, the third mask has a structure where a shielding portion and adiffractive exposure portion repeat at the rest area except for thetransmission portion. The organic film 24 remaining in correspondencethereto is patterned to have a structure that a shielding area(projected portion) and a diffractive exposure area (groove portion)having a stepped difference are repeated. Subsequently, the organic film24 where the projected portion and the groove portion are repeated isfired so that the surface of the organic film 24 has the embossingshape.

As shown in FIG. 2D, a second passivation film 26 is formed on theorganic film 24 that has the embossing shape, and the reflectionelectrode 28 is formed on top thereof by a fourth mask process. Thesecond passivation film 26 and the reflective metal layer are depositedto maintain their embossing shape on top of the organic film 24 that hasthe embossing surface. The second passivation film 26 is formed of aninorganic insulating material such as the first passivation film 22, andthe reflective metal layer is formed of a metal such as AlNd or thelike, of which the reflectivity is high. Subsequently, the reflectivemetal layer is patterned by a photolithography process using a fourthmask and the etching process to form the reflection electrode 28. Here,the reflection electrode is independent of every pixel and is opened atthe transmission hole 36 and the open hole 35 of the organic film 24.

As shown in FIG. 2E, a third passivation film 30 covering the reflectionelectrode 28 is formed by a fifth mask process, and the contact hole 34penetrating the first to third passivation films 22, 26, 30 is formed.The third passivation film 30 covering the reflection electrode 28 isformed and the contact hole 34 is formed by a photolithography processusing a fifth mask and the etching process. Here, the contact hole 34penetrates the first to third passivation films 22, 26, 30 at the openhole 35 of the organic film 24. The contact hole 34 exposes the drainelectrode 18 and the upper storage electrode 20. The third passivationfilm 30 is formed of the same inorganic insulating material as thesecond passivation film 26.

As shown in FIG. 2F, a pixel electrode 32 is formed on the thirdpassivation film 30 using a sixth mask process. A transparent conductivelayer is formed on the third passivation film 30 by the depositionmethod such as sputtering, and the transparent conductive layer ispatterned by a photolithography process using a sixth mask and theetching process to form the pixel electrode 32 at each pixel area. Thepixel electrode 32 is connected to the upper storage electrode 20through the contact hole 34. The transparent conductive layer is formedof indium-tin-oxide ITO.

In this way, the related art transflective thin film transistorsubstrate is formed by six mask processes, thereby complicating itsmanufacturing process is complicated.

SUMMARY OF THE INVENTION

Accordingly, the present invention is directed to a liquid crystaldisplay device and fabricating method thereof that substantiallyobviates one or more of the problems due to limitations anddisadvantages of the related art.

An object of the present invention to provide a transflective thin filmtransistor substrate and a method of fabricating the same with asimplified process.

Additional features and advantages of the invention will be set forth inthe description which follows, and in part will be apparent from thedescription, or may be learned by practice of the invention. Theobjectives and other advantages of the invention will be realized andattained by the structure particularly pointed out in the writtendescription and claims hereof as well as the appended drawings.

To achieve these and other advantages and in accordance with the purposeof the present invention, as embodied and broadly described, a liquidcrystal display device comprises a first substrate a gate line on thefirst substrate; a first insulation film on the gate line; a data linecrossing the gate line such that the data line and the gate line definea pixel region with a transmission area and a reflection area; a thinfilm transistor connected to the gate line and the data line; a storagecapacitor including a storage line crossing the data line, and an upperstorage electrode being connected to the thin film transistor andoverlapping the storage line; a second insulation film on the thin filmtransistor, a transmission hole being defined through the secondinsulation film; a reflection electrode disposed on the secondinsulation film in the reflection area and connected to a portion of theupper storage electrode through the transmission hole; a pixel electrodedisposed in the pixel region and connected to the reflection electrode;a second substrate facing the first substrate; and a liquid crystallayer disposed between the first and second substrates.

In another aspect, a method of fabricating a liquid crystal displaydevice comprises forming a gate pattern on a first substrate using afirst mask, the gate pattern including a gate line, a gate electrodeconnected to the gate line, and a storage line; forming a firstinsulation film on the gate pattern, a semiconductor pattern on thefirst insulation film, and a source/drain pattern having a data line, asource electrode, a drain electrode, and an upper storage electrodeusing a second mask, the data and gate lines crossing each other todefine a pixel region with a transmission area and a reflection area;forming a second insulation film on the source/drain pattern using athird mask, the second insulation film defining a transmission holethrough the second insulation film; forming a reflection electrode inthe reflection area using a fourth mask, the reflection electrode beingconnected to a portion of the upper storage electrode through thetransmission hole; forming a third insulation film on the reflectionelectrode and a pixel electrode using a fifth mask, the pixel electrodebeing connected to the reflection electrode; and joining the firstsubstrate with a second substrate and disposing a liquid crystal layerbetween the first and second substrates.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory and areintended to provide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this specification, illustrate embodiments of the invention andtogether with the description serve to explain the principles of theinvention. In the drawings:

FIG. 1 is a sectional view illustrating a portion of a related arttransflective liquid crystal display panel;

FIGS. 2A to 2F are sectional views explaining sequentially a fabricatingmethod of the transflective thin film transistor substrate shown in FIG.1;

FIG. 3 is a plane view partially illustrating a transflective thin filmtransistor substrate according to an embodiment of the presentinvention;

FIG. 4 is a sectional view illustrating the transflective thin filmtransistor substrate taken along lines II-II′, III-III, IV-IV′ of FIG.3;

FIGS. 5A and 5B are a plane view and a sectional view describing a firstmask process of the transflective thin film transistor substrateaccording to the present invention;

FIGS. 6A and 6B are a plane view and a sectional view describing asecond mask process of the transflective thin film transistor substrateaccording to the present invention;

FIGS. 7A and 7E are sectional views describing a second mask processaccording to the present invention;

FIGS. 8A and 8B are a plane view and a sectional view describing a thirdmask process of the transflective thin film transistor substrateaccording to the present invention;

FIGS. 9A and 9B are a plane view and a sectional view describing afourth mask process of the transflective thin film transistor substrateaccording to the present invention;

FIGS. 10A and 10B are a plane view and a sectional view describing afifth mask process of the transflective thin film transistor substrateaccording to the present invention; and

FIGS. 11A and 11D are sectional views describing the fifth mask processof the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference will now be made in detail to the preferred embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings.

Hereinafter, the preferred embodiment of the present invention will bedescribed in detail with reference to FIGS. 3 to 11D.

FIG. 3 is a plane view partially illustrating a transflective thin filmtransistor substrate according to an embodiment of the presentinvention, and FIG. 4 is a sectional view illustrating the transflectivethin film transistor substrate taken along lines II-II′, III-III, IV-IV′of FIG. 3.

As shown in FIGS. 3 and 4, the transflective thin film transistorsubstrate includes a lower substrate 142; a gate line 102 and a dataline 104 that define a pixel area on the lower substrate 142 crossingeach other with a gate insulating film 144 therebetween; a thin filmtransistor 106 connected to the gate line 102 and the data line 104; areflection electrode 152 formed at a reflection area of each pixel; anda pixel electrode 118 formed at each pixel area and connected to thethin film transistor 106 through the reflection electrode 152 and anupper storage electrode 122. The transflective thin film transistorsubstrate includes a storage capacitor 120 formed by overlapping astorage line 150 with the upper storage electrode 122 connected to thepixel electrode 118 via the reflection electrode 152; a gate pad 124connected to the gate line 102; and a data pad 134 connected to the dataline 104. The transflective thin film transistor substrate divides eachpixel area into a reflection area where the reflection 15, electrode 152is formed and a transmission area where the reflection electrode 152 isnot formed.

The thin film transistor 106 includes a gate electrode 108 connected tothe gate line 102; a source electrode 110 connected to the data line104; a drain electrode 112 facing the source electrode 110 to beconnected to the pixel electrode 118; an active layer 114 overlappingthe gate electrode 108 with a gate insulating film 144 therebetween toform a channel between the source electrode 110 and the drain electrodes112; and an ohmic contact layer 116 formed on the active layer 114except for a channel portion to make an ohmic contact with the sourceelectrode 110 and the drain electrode 112. The thin film transistor 106responds to the scan signal of the gate line 102 to cause a video signalon the data line 104 to be charged and maintained in the pixel electrode118. A semiconductor pattern 115 including the active layer 114 and theohmic contact layer 116 is formed to overlap the data line 104 as well.

The reflection electrode 152 is formed at the reflection area of eachpixel to reflect an external light. The reflection electrode 152 has theembossing shape in accordance with the shape of the organic film 148,thereby increasing its reflection efficiency due to its dispersioneffect. Further, the reflection electrode 152 is connected via atransmission hole 150 penetrating the organic film 148 to a side surfaceof the upper storage electrode 122.

The transmission hole 154 is formed at the transmission area topenetrate a gate insulating film 144, the organic film 148, thereflection electrode 152, and the passivation film 146. Accordingly, thelength of the light path that runs through the liquid crystal layerbecomes the same at the reflection area and the transmission area. Thus,the transmission efficiency of the reflection mode and the transmissionmode becomes the same. As the transmission hole goes from the gateinsulating film 144 to the passivation film 146, its width becomeswider. Accordingly, the reflection electrode 152 formed at a reflectionarea is practically exposed.

The pixel electrode 118 independently formed at each pixel areaoverlapping with a partial portion of the reflection electrode 152exposed through the transmission hole 154 and is connected. Accordingly,the pixel electrode 118 is connected to the reflection electrode 152 ofthe pixel electrode 118, and to the drain electrode 112 of the thin filmtransistor 106 via the upper storage electrode 122 connected to thereflection electrode 152. The pixel electrode 118 generates a potentialdifference with a common electrode of a color filter (not shown) by apixel signal supplied through the thin film transistor. The potentialdifference causes liquid crystal molecules having dielectric anisotropyto rotate, thereby controlling the transmissivity of the light that runsthrough a liquid crystal layer in each of the reflection area and thetransmission area. Thus, its brightness is changed in accordance withthe video signal. Herein, an opening portion of the passivation film 146overlaps with a partial transmission hole 154 and a partial reflectionelectrode 152 adjacent to the transmission hole 154. Further, thepassivation film 146 forms a boundary from the pixel electrode 118.

The storage line 150 adjacent to the gate line 102 and crossing the dataline 104 overlaps the upper storage electrode 122 connected to the pixelelectrode 118 with the gate insulating film 144 therebetween, therebyforming the storage capacitor 120. The upper storage electrode 122 isintegrated with the drain electrode 112, and is connected to the pixelelectrode 118 through the reflection electrode 152. The upper storageelectrode 112 further overlaps the semiconductor pattern 115 under theupper storage electrode 122.

The gate line 102 is connected to a gate driver (not shown) through thegate pad 124. The gate pad 124 includes a lower gate pad electrode 128extended from the gate line 102; and an upper gate pad electrode 130connected to the lower gate pad electrode 128 via a contact hole 126penetrating through the passivation film 146 and the gate insulatingfilm 144.

The data line 104 is connected to a data driver (not shown) through thedata pad 134. The data pad 134 includes a lower data pad electrode 138extended from the data line 104; and an upper data pad electrode 130connected to a side surface of the lower data pad electrode 138 via asecond contact hole 136 penetrating the passivation film 146, the lowerdata pad electrode 138, and the semiconductor pattern 115.

In the transflective thin film transistor substrate having the abovestructure, a transparent conductive pattern including the pixelelectrode 118, the upper gate pad electrode 130, and the upper data padelectrode 140 is formed by the same patterning process of thetransparent conductive layer. In this case, the transparent conductivelayer is patterned by the lift-off process removing the photoresistpattern used in forming the transmission hole 154, the first hole 126,and the second contact hole 136. The transmission hole 154, the firsthole 126, and the second contact hole 136 penetrate from passivationfilm 146 to the gate insulating film 144 in the previous process.Accordingly, the transparent conductive pattern forms a boundary from anedge portion of the passivation film 146.

As a result, the transflective thin film transistor substrate accordingto the embodiment of the present invention is formed by the followingfive mask processes. FIGS. 5A and 5B are a plane view and a sectionalview explaining a first mask process in a fabricating method of thetransflective thin film transistor substrate according to the embodimentof the present invention.

A gate pattern is formed by a first mask process where the gate patternincludes the gate line 102, the gate electrode 108 connected to the gateline 102, the lower gate pad electrode 128, and the storage line 150 onthe lower substrate 142. More particularly, the gate metal layer isformed on the lower substrate by a deposition method such as sputtering.The gate metal layer is patterned by a photolithography process using afirst mask and an etching process, thereby forming the gate pattern thatincludes the gate line 102, the gate electrode 108, the lower gate padelectrode 128, and the storage line 150. The gate metal layer is formedof a metal material such as Mo, Cu, Al(Nd), Cr, Ti, MoW, Ta or the like.Further, the gate metal layer can be formed with a double layer having afirst conductive layer and a second conductive layer, wherein the firstconductive layer is formed of ITO, TO, IZO or the like and the secondconductive layer is formed of a metal material as mentioned above.

FIGS. 6A and 6B are a plane view and a sectional view explaining asecond mask process in a fabricating method of the transflective thinfilm transistor substrate according to the present invention. FIGS. 7Ato 7E are sectional views specifically explaining the second maskprocess.

The gate insulating film 144 is formed on the lower substrate 142 wherethe gate pattern is formed. A source/drain pattern including the dataline 104, the source electrode 110, the drain electrode 112, the upperstorage electrode 122 and the lower data pad electrode 138, asemiconductor pattern 115 including the active layer 114 and the ohmiccontact layer 116 that overlap along the rear surface of thesource/drain pattern are formed on top thereof by a second mask process.The semiconductor pattern 115 and the source/drain pattern are formed bya one mask process using a diffractive exposure mask.

Specifically, the gate insulating film 144, an amorphous silicon layer105, an amorphous silicon layer 107 doped with impurities n+ or p+, asource/drain metal layer 109 are sequentially formed on the lowersubstrate 142 where the gate pattern is formed as in FIG. 7A. Forexample, the gate insulating film 144, the amorphous silicon layer 105,the amorphous silicon layer 107 doped with impurities are formed byPECVD, and the source/drain metal layer 109 is formed by sputtering. Thegate insulating film 144 is formed of inorganic insulating material suchas silicon oxide SiOx, silicon nitride SiNx and like. The source/drainmetal layer 109 is formed of metal material such as Mo, Cu, Al(Nd), Cr,Ti, MoW, Ta or the like.

A photoresist 219 is spread over the source/drain metal layer 109, andthen the photoresist 219 is exposed and developed by a photolithographyprocess using a diffractive exposure mask 210, thereby forming aphotoresist pattern 220 having the stepped difference as shown in FIG.7B. The diffractive exposure mask 210 includes a transparent quartzsubstrate 212, a shielding layer 214 on top of the substrate 212 formedof a metal layer such as Cr and CrOx and the like, and a diffractiveexposure slit 216. The shielding layer 214 is located at an area wherethe semiconductor pattern and the source/drain pattern are to be formedto intercept ultraviolet ray, thereby leaving a first photoresistpattern 220A after development. The diffractive exposure slit 216 islocated at an area where the channel of the thin film transistor is tobe formed to diffract the ultraviolet ray, thereby remaining a secondphotoresist pattern 220B that is thinner than the first photoresistpattern 220A after development.

Subsequently, the source/drain metal layer 109 is patterned by theetching process using the photoresist pattern 220 having a steppeddifference, thereby forming the source/drain pattern and thesemiconductor pattern 115 thereunder as shown in FIG. 7C. In this case,the source electrode 110 and the drain electrode 112 in the source/drainpattern have a structure where they are integrated.

Then, the photoresist pattern 220 is ashed by an ashing process using anoxygen O₂ plasma. Thus, the first photoresist pattern 220A becomesthinner and the second photoresist pattern 220B is removed as shown inFIG. 7D. The source/drain pattern exposed by the removal of the secondphotoresist pattern 220B and the ohmic contact layer 116 thereunder areeliminated by the etching process using the ashed first photoresistpattern 220A, thereby separating the source electrode 110 from the drainelectrode 112 and exposing the active layer 114. Accordingly, a channelof the active layer 114 is formed between the source electrode 110 andthe drain electrode 112. At this moment, both sides of the source/drainpattern are etched once more along the ashed first photoresist pattern220A, thus the source/drain pattern and the semiconductor pattern 115have a fixed stepped difference in a step shape.

Then, the first photoresist pattern 220A remaining on the source/drainpattern is removed by a strip process as in FIG. 7E.

FIGS. 8A and 8B are a plane view and a sectional view explaining a thirdmask process in a fabricating method of the transflective thin filmtransistor substrate according to the present invention.

On the gate insulating film 144 having the source/drain pattern formedby the third mask process, the transmission hole 154 is formed at thetransmission area and the organic film 148 (having an embossing surfaceat the reflection area) removed at the pad area is formed. Specifically,the organic film 148 is formed on the gate insulating film 144 havingthe source/drain pattern by spin coating. The organic film 148 is formedof a photosensitive organic material such as acrylic resin. Then, theorganic film 148 is patterned by the photolithography process using thethird mask, that is, a half tone mask or a diffractive exposure mask.Thus the transmission hole 155 penetrating the organic film 148 isformed in the transmission area in correspondence to the transmissionportion of the third mask, and the organic film 148 is removed at thepad area. Further, the remaining portion except for the transmissionportion in the third mask has a structure that the shielding portion andthe diffractive exposure portion (or transflective portion) arerepeated. In correspondence thereto, the organic film 148 is patternedto have a structure where the shielding area (projected portion) and thediffractive exposure area (groove portion) having the stepped differenceare repeated in the reflection area. Subsequently, the organic film 148with the repeated projected portion and groove portion is cured to formthe embossing shape on the surface of the organic film 148.

FIGS. 9A and 9B are a plane view and a sectional view explaining afourth mask process in a fabricating method of the transflective thinfilm transistor substrate according to the present invention.

The reflection electrode 152 is formed at each pixel reflection area bythe fourth mask process. Specifically, a reflective metal layer havingan embossing surface is formed on the organic film 148 and maintains theembossing shape. The reflective metal layer is formed of a metal thathas a high reflectivity like AlNd. Subsequently, the reflective metallayer is patterned by a photolithography process using the fourth maskand the etching process, thereby independently forming the reflectionelectrode 152 at every reflection area of each pixel. The reflectionelectrode 152 is connected to the drain electrode 112 via a side surfaceof the upper storage electrode 122 exposed at the edge portion of thetransmission hole 154.

FIGS. 10A and 10B are a plane view and a sectional view explaining afifth mask process in a fabricating method of the transflective thinfilm transistor substrate according to of the present invention, FIGS.11A and 11D are sectional views to specifically describe the fifth maskprocess of the present invention.

In the fifth mask process, the transmission hole 154 penetrates from thepassivation film 146 through the gate insulating film 144; the first andthe second contact holes 126 and 136 exposing the lower gate padelectrode 128 and the lower data pad electrode 138 are formed; and atransparent conductive pattern including the pixel electrode 118, theupper gate pad electrode 130 and the upper data pad electrode 140 isformed.

Specifically, as shown in FIG. 11A, the passivation film 146 coveringthe reflection electrode 152 is formed by the deposition method such asPECVD. A photoresist pattern 230 is formed on the passivation film 146by a photolithography process. The passivation film 146 is of aninorganic insulating material like that used for the gate insulatingfilm 144. The photoresist pattern 230 has an opened structure at thearea having the transmission hole 154, the lower gate pad electrode 128and the lower data pad electrode 138.

The passivation film 146 and the gate insulating film 144 are patternedby the etching process using the above photoresist pattern 230 so thatthe transmission hole 154 penetrates the passivation film 150 and thegate insulating film 144 as shown in FIG. 11B, and the first and thesecond contact holes 126 and 136 exposing the lower gate pad electrode128 and the lower data pad electrode 138 are formed. The transmissionhole 154 exposes a partial reflection electrode 152. The first contacthole 126 penetrates the passivation film 146 and the gate insulatingfilm 144 to expose the lower gate pad electrode 128. The second contacthole 136 penetrates the passivation film 146, the lower data padelectrode 138 and the semiconductor pattern 115 to expose a side surfaceof the lower data pad electrode 138. In this case, the edge part of thephotoresist pattern 230 has more projected shape than the edge part ofthe passivation film 146 due to the over-etched passivation film 146.The ashing process and the etching process are continually performed inthe same chamber.

Subsequently, a transparent conductive film 117 is entirely on the thinfilm transistor substrate having the photoresist pattern 230 by adeposition method such as sputtering. The transparent conductive film117 is formed of ITO, TO, IZO or the like. At this time, the transparentconductive film 117 deposited having a straight property by the edgeportion of the projected photoresist pattern 230 is opened at the edgeportion of the passivation film 146 to form a stripper osmosis path.

The photoresist pattern 230 and the transparent conductive film 117 onthe photoresist pattern 230 are removed together by the lift-offprocess, thereby forming the transparent conductive pattern includingthe pixel electrode 118, the upper gate pad electrode 132 and the upperdata pad electrode 140, as shown in FIG. 11D. At this time, because thestripper is easily passed into the edge part of the passivation film 146via the osmosis path formed by open of the transparent conductive film117, lift-off efficiency can be improved. The pixel electrode 118 formsa boundary from the passivation film 146 in the transmission hole 154.The pixel electrode 118 is connected to the exposed reflection electrode152. The upper gate pad electrode 130 forms a boundary from thepassivation film 146 in the first contact hole 126 to connected to thelower gate pad electrode 128. The upper data pad electrode 140 forms aboundary from the passivation film 146 in the second contact hole 136 toconnected to a side surface of the lower data pad electrode 138.

As described above, in the transflective thin film transistor substrateand the method of driving the same, the transparent conductive patternis formed by the lift-off process of the photoresist pattern used informing the transmission hole and the contact hole that penetrate thepassivation film and the gate insulating film, thereby simplifying theprocesses by performing a five mask process.

It will be apparent to those skilled in the art that variousmodifications and variations can be made in the liquid crystal displaydevice and fabricating method thereof of the present invention withoutdeparting from the spirit or scope of the invention. Thus, it isintended that the present invention cover the modifications andvariations of this invention provided they come within the scope of theappended claims and their equivalents.

1. A liquid crystal display device, comprising: a first substrate; agate line on the first substrate; a first insulation film on the gateline; a data line crossing the gate line such that the data line and thegate line define a pixel region with a transmission area and areflection area; a thin film transistor connected to the gate line andthe data line; a storage capacitor including a storage line crossing thedata line, and an upper storage electrode being connected to the thinfilm transistor and overlapping the storage line; a second insulationfilm on the thin film transistor, a transmission hole being definedthrough the second insulation film; a reflection electrode disposed onthe second insulation film in the reflection area and connected to aportion of the upper storage electrode through the transmission hole; apixel electrode disposed in the pixel region and connected to thereflection electrode; a second substrate facing the first substrate; anda liquid crystal layer disposed between the first and second substrates.2. The device of claim 1, further comprising a third insulation filmabsent from the transmission area of the pixel region and a portion ofthe reflection electrode where the pixel electrode is connected to thereflection electrode.
 3. The device of claim 2, wherein the pixelelectrode forms contacts with the third insulation film to define aboundary of the transmission hole.
 4. The device of claim 2, furthercomprising a gate pad having a lower gate pad electrode and an uppergate pad electrode, the lower gate pad electrode being extended from thegate line and the upper gate pad electrode being connected to the lowergate pad electrode via a contact hole through the third insulation filmand the first insulation film.
 5. The device of claim 4, wherein theupper gate pad electrode abuts the third insulation film in the contacthole.
 6. The device of claim 4, wherein the second insulation film inthe reflection area is absent in the gate pad.
 7. The device of claim 2,further comprising a data pad having a lower data pad electrode and anupper data pad electrode, the lower data pad electrode being extendedfrom the data line and the upper data pad electrode connected to thelower data pad electrode via a contact hole through the third insulationfilm and the lower data pad electrode.
 8. The device of claim 7, whereinthe contact hole forms a channel of the thin film transistor andpenetrates to a semiconductor pattern extended to the lower data padelectrode along the data line.
 9. The device of claim 7, wherein theupper data pad electrode abuts the third insulation film in the contacthole.
 10. The device of claim 7, wherein the second insulation film inthe reflection area is absent in the data pad.
 11. The device of claim7, wherein the upper data pad electrode is laterally connected to thelower data pad electrode.
 12. The device of claim 1, wherein thetransmission hole is further defined to pass through the firstinsulation film in the transmission area.
 13. The device of claim 1,wherein the second insulation film has an embossing surface in thereflection area.
 14. The device of claim 1, wherein the secondinsulation film includes an organic material.